Foundation Design using SAFE
1. Model the isolated footing provided in week 11 challenge on SAFE. Analyze and design it to verify the size, depth and steel provided as per calculations.
2. A column of size 600x600 carrying an unfactored gravity load (DL+LL) of 1175 KN is to be supported on pile cap, which ultimately transfers load to the piles underneath. Piles of 16 metres length and 500 mm diameter are to be used. Each pile has a load carrying capacity of 200 KN. Model, analyse and design the pile cap on SAFE to evaluate the following:
- Pile group to be used
- Depth of pile cap
- Longitudinal steel on top and bottom face in both directions
Note: Participants must refer to IS 2911 (part 2) and SP 34 for 2nd challenge
1. Model the isolated footing provided in week 11 challenge on SAFE. Analyze and design it to verify the size, depth and steel provided as per calculations.
AIM: Model the isolated footing provided in week 11 challenge on SAFE. Analyze and design it to verify the size, depth and steel provided as per calculations.
INTRODUCTION:
* CSI SAFE (Slab Analysis by the Finite Element Method) is the best tool for designing concrete slabs and foundations.
* SAFE provide easiness to engineer towards the safe design of structures with powerful tools like draw, analyze, design and detailing etc.
Laying out models is quick and efficient way with the user-friendly drawing tools, or user can import model layouts from AutoCAD or loading conditions from other software’s like CSI ETABS and CSI SAP2000.
PROCEDURE:
Step:1- Open SAFE and Create New model:
- Open the SAFE Application and select New Model followed by Input Settings, Units was selected as Metric and Code IS 456-2000.
- Provide Clear cover for top and bottom and bar size.
Step:2- Calculation for Subgrade model and unfactored load:
Step:3- Provide paln dimensions and Load:
Step:4- Define materials:
- Calculate E for concrete:
- Select Define - go to Material properties
- Click on add new material
- M25 concrete added as shown in next
- Fe 500 Rebar was added next as shown
Step:5- Define slab properties
- Go to define tab - select slab properties
- Slab properties was defined next as shown
Step:6- Define soil properties:
- Define - soil properties - add new properties
- Soil properties was added next as shown
- In order to open the properties right click on the footing
Step:7- Assign Load properties:
- Assign - load load data - point load
- Both dead and live load patterns was defined next
Step:8- Create Load case combination:
- Define - load combination - add new combo
- Load case combination was defined next
Step:8- Run analysis:
- Analysis was performed next
1) As displacement is -12 mm which is less than 25 mm ............Safe
2) Check for Bearing Pressure
i) For that Click On Display - Soil Pressure - Select Combination as - ULS
ii) As we can see that Bearing pressure is more than SBC
i.e 169.22kn/m2 > 150 kN/m2 ..........................Unsafe
iii) We have to Increase the area to see if we can reduce the bearing pressure below the SBC
iv) Now provide the area as 4m x 4m
v) Here we can see that after increasing the area Bearing pressure is reduced
i.e -143.30 < 150>
3) Check of Punching Shear
i) Click on Display - Punching Shear
ii) As we can see that Punching shear is less than 1
i.e 0.39 <1>
Step:9- Design strips:
- Design strip was added next and Analysis was performed.
- Edit - add/ edit strip - add design strips
- The slab design is as shown below
Result:
- Isolated footing was designed using SAFE
2. A column of size 600x600 carrying an unfactored gravity load (DL+LL) of 1175 KN is to be supported on pile cap, which ultimately transfers load to the piles underneath. Piles of 16 metres length and 500 mm diameter are to be used. Each pile has a load carrying capacity of 200 KN. Model, analyse and design the pile cap on SAFE to evaluate the following:
- Pile group to be used
- Depth of pile cap
- Longitudinal steel on top and bottom face in both directions
AIM:
To Model, analyze and design the pile cap on SAFE to evaluate the following:
- Pile group to be used
- Depth of pile cap
- Longitudinal steel on top and bottom face in both direction
Step:1-Open SAFE and Create new model:
- Open the SAFE Application and select New Model followed by Input Settings, Units was selected as Metric and Code IS 456-2000.
- 50mm each was provided as cover at top and bottom and Bar size was defined as 16mm
Step:2-Define Coordinates:
- Coordinates was defined next:
- Grid spacing in X direction and Y direction was taken as 2.9m and 1.65m respectively.
- It’s shown in the below figure too.
Step:3-Material Property data:
- Click define followed by Material properties
- M25 grade of concrete
- Modulus of elasticity, E = X 5000 = 25000N/mm^2
- Fe 500 Rebar was added next as shown
Step:4- Define Slab propetries:
- Slab properties was defined next as shown
- Pile Cap, Column and pile details was defined.
Step:5- Create Geometry:
- Now slabs are to be added to the model
- Draw points
- Piles was added and edge distance was modified to 0.3m
- The column was created of size 600mm X600mm in the center using the draw option now.
Step:6- Add springs:
- Springs was added next
- Piles- Assign – Support Data – point springs
- Spring Constant from above calculation is taken as
Step:7- Assign Loads:
- Dead and Live load of 587.5KN are added next
Step:8- Create load combinations:
- Load case combination was defined next
Step:9- Run Analysis:
- After defining the load combination run the analysis.
- Maximum displacement was found to be .840, so it’s safe
- Also, all the punching shear values are less than 1, So its safe
- Joint Reaction Diagram
- As all the reaction forces are according to the limit, Its safe
Step:10- Add design strips:
- Reinforcement details are added next as shown in both X and Y direction respectively and run the analysis again.
Reinforcement slab design:
Pile Cap foundation design
Result
- Completed design of Pile cap foundation using SAFE software